Wound dressings of the type outlined above that have been used in the past invariably have a woven or non-woven fibrous sheet of material forming the surface of the dressing that actually contacts the wound in use.
The disadvantage of this arrangement is that there is a distinct tendency for the fibrous sheet of material to become stuck to the wound and this can have a seriously deleterious effect when the time arrives to remove the dressing. Indeed, a patient can be subjected to substantial pain during the removal process and a considerable amount of good that has been achieved as regards the healing process can be lost. This situation is generally not improved by interposing a layer of lint, or other fibrous material, typically a fabric pad or the like, between the wound and the dressing as the lint or fibres of the pad can then become stuck to the wound. In addition, in such a removal process granulation tissue can be destroyed and this generally retards the healing process.
Reverting now to the treatment compositions, in my said earlier patent applications I describe wound treatment compositions that are composed of two basic ingredients, namely, an anti-septic or antimicrobial agent and a desiccant by which term is meant a compound operating on the basis of adsorption rather than one of absorption. The preferred compositions have included sodium chloride or sucrose as the antimicrobial agent, and silica gel as the desiccant.
Whilst these compositions operate effectively from a medical and thus healing point of view they have certain disadvantages from the point of view that the sodium chloride or sucrose tends to become dissolved to some extent in the moisture being adsorbed. As a consequence the sodium chloride or sucrose can tend to migrate through the moisture permeable membrane that generally forms part of an envelope containing the composition and which is supposed to form a barrier between the composition and the wound itself. The consequence of this is that, in the case of sodium chloride, the patient suffers considerable pain in consequence of sodium chloride entering the wound. In both cases there has also been a tendency for the composition to stick to the wound to some extent thereby causing difficulties in removal of the dressing and this represents another possible source of pain to the patient.
Collagen is widely used as a direct wound treatment composition. Numerous different methods and vehicles for Its application to wounds have been proposed and used such as application directly to the wound in particulate form; in the form of a suspension; in the form of a gel, optionally in combination with other active ingredients such as iodine; as an exposed layer in the central area of an adhesive dressing; and as an active ingredient of a spray for application to a wound.
Prior U.S. Pat. No. 5,800,372 discloses a field dressing in which collagen is used to promote blood clotting in fresh wounds in order to stem the bleeding and propagate blood clotting backwards towards the wound. The collagen is mixed with a super absorbent polymer that serves to absorb a large quantity of liquid contained in the blood.
It has now surprisingly been found that the beneficial effects of collagen can be exploited in what applicant believes to be a novel and surprisingly effective manner.